Pump control means for hydraulic systems



Dec. 7, 1948.

J IEr.1

G. A. WALDIE PUMP CONTROL MEANS FOR HYDRAULIC SYSTEMS Filed Nov. 27, 1942 I 1"? x 4 5 Z J m 7/ 41 T my n J3 ST z 6 I 7 O 39.- Z

\ INVENTOR 'GEORGE A.WALD|E mama";

ATTORNEYv Patented Dec. 7, 1948 UNITED" STATES PATENT OFFICE PUMP CONTROL MEANS FOR HYDRAULIC SYSTEMS 2 Claims. 1 This invention relates to control systems and, in particular, to control systems for pressure fluid sources, such as pumps.

It is an object of this invention to provide an improved control system in connection with a fluid pressure pump, which will allow the pump to run idle under substantially no load.

It is another object of the invention to provide' a hydraulic system including fluid operable motor means and a fluid pressure source for delivering pressure fluid to said motor means, in which the fluid source is provided with control means operable to allow said fluid source to idle under substantially no load.

Another object of the invention consists in the provision of a hydraulic system including hydraulically operable motor means and a variable delivery pump for delivering pressure fluid to said motor means, in which the pump is provided with fluidpressure responsive means operable selectively by fluid delivered by said pump for moving the pump into substantially neutral or no delivery position.

It is a further object of the invention to provide a hydraulic system including a fluid source of constant delivery, in which fluid pressure responsive means is provided operable selectively by fluid delivered by said fluid source for by-passing the delivery of said fluid source.

Still another object of the invention consists in the provision of a hydraulic system including a variable delivery pump for supplying pressure fluid, in which first fluid pressure responsive means is adapted in response to a predetermined pressure to shift the pump into substantially neutral or no delivery position, and in which second fluid pressure responsive means, independent of said first fluid pressure responsive means, is provided for moving said pump into subtantially neutral or no delivery position during any time Figure 2 is a slight modification of a detail in Figure 1 and comprises an additional control feature.

Figure 3 is a further embodiment of 'the inven 'be connected with the main supply line I l.

,mcunted therein a press ram 2. The upper portion of the cylinder l communicates with a conduit 3 leading to a four-way valve 4, of any standard design.

Branching off from the conduit 3 is a conduit 5 comprising a tonnage control valve 6 which, in response to a predetermined pressure in the conduit 5, closes a normally open switch 'I. The tonnage control valve 6 may be of any standard design, for instance, of the type set forth in U. S. Patent No. 2,224,957. 7

One terminal of the switch I is connected through the line 8 with the line 9, which latter is adapted, by closure of the starter switch III, .to The main supply line I2 is connected through a normally closed starter switch ST and the line i3 The valve member I5 comprises two intercontion in connection with a constant delivery pump. I

Referring now to the drawings in detail, I designates a press cylinder having reciprocably nected piston portions l8 and 19 reciprocably mounted in the valve cylinder 20 for controlling fluid connection between the conduits 2|, 22 and 23.

As will be clear from the drawing, t e conduit 2| communicates with the conduit 23, when the valve member l5 occupies the position shown'in Figure 1. When the valve member 15 is in its right hand end position, the conduit 23 communicates with the conduit 22, while the fluid connection between the conduits 2| and 23 is interrupted.

The conduit 2| leads into the conduit 24 which connects the pressure side of the variable delivery pump 25 with the valve 4. The pump 25 may be of any standard design, preferably of the.

radial piston or the radial vane type. The suction side of the pump 25 communicates through the conduit 26 with a fluid reservoir or tank 21. Branching off from the conduit 26 is a conduit 28 leading to the valve 4. Also connected to the valve 4 is a conduit 29 communicating with the lower portion of the cylinder l.

The valve 4 is adapted to be actuated so as to effect fluid connection between the conduit 24 and the conduit 3, while simultaneously connecting the conduits 28 and 29 with each other. The valve 4 is also operable to effect fluid connection between the conduits 24 and ,29, while simultaneously connecting the conduits 3 and 28 with each other.

The pump 25 has connected thereto, on one side thereof, a cylinder 33, in which is reciprocably mounted a plunger 3| connected with the fiow control member (not shown) the pump 25. Movement of the plunger 3| toward the right shifts the flow control member 0! the pump 25 so as to reduce the delivery of the pump, when the plunger 3| has reached its extreme right hand position, the pump 25 is in substantially neutral or no delivery position. The left handend oi the cylinder 3|) is connected through a pilot line 32 with the pressure line 24.

The pump 25 has also connected thereto a cylinder 33 in which is reciprocably mounted a plunger 34, likewise connected with the flow control member of the pump 25 and adapted, when moved toward the leit, to shift the pump 25 into position in delivery. The efl'ective area of the plunger 34 equals the eflective area of the plunger 3|.

Arranged between the plunger 34 and the right hand end of the cylinder 33 is a spring 35, which line 39 with the terminal 43. The terminal 43 is adapted, by closure oi the switch 68, to be connected with the line 42, which latter is connected with the main supply line H. The. line 42 is turthermore adapted, by closure of the switch 43, to be connected with the line 44. Closure of the switch 45 is adapted to eflect electric connection between the line 42 and the line 43 leading to one terminal of a switch 41, the other terminal of which is connected to the line 3.

Operation of first embodiment elective. To this end, the switch 43 is in open der I, this pressure is conveyed through the conduits 3 and 5 to the tonnage. control valve 3 and actuates the latter so as to close the normally open switch 1. As a result thereof, the energizing circuit for the solenoid i4 is closed, which circuit comprises the main supply line i2, starter switch BT, line l3, solenoid i4, lines 3 and 3, now closed switch 1, line 44, switch 43, line 42 and main supply line H.

Energization oi the solenoid |4 causes the valve member I! to move to its right hand end position in which fluid connection is interrupted between the conduits 2| and 23, while the conduit 231s connected with the conduit 22. Consequently, since the pump 25 still conveys fluid pressure through conduit 32 into the cylinder 30, while the cylinder 33 is now connected with the tank 21, the pressure acting upon the plunger 3| moves the latter toward the right, thereby shifting the pump 25 into substantially neutral or no delivery position. Therefore, the ram 2 comes to a stop, while the pump 23 idles under substantially no load.

In order to start a retraction stroke of the ram 2, the operator reverses the valve-4 so as to eil'ect fluid connection between the conduits 24 and 23, while connecting the conduits 3 and 23 with each other. This causes a pressure'drop in the conduit 24 so that the spring 33 again shifts the pump 25 on stroke. Furthermore, the operator opens the starter switch sT which breaks the energizing circuit for the solenoid i4. As a result thereof, the spring |1 moves the valve member i3 into the position shown in Figure 1.

Pressure fluid delivered by the pump 25 now It may be assumed that all parts occupy the 1 position shown in Figure l, which is the position immediately following the initiation of .a downward stroke of the ram 2. In this position, the pump 25 is on full delivery stroke and the valve member l3 effects fluid connection between the conduits 2| and 23, while the valve 4 connects the conduits 24 and 3 with each other, and establishes fluid connection between the conduits 23 and 29. Pressure fluid irom the pump 23, therefore, passes through the conduits 32 and 2| and into the cylinders 33 and 33 respectively, where it acts upon the plungers 3| and 34. However-{inasmuch as the areas of these plungersequal each other, these plunger-s remain in the position shown in Figure 1, into which they were moved by the spring 35.

Pressure fluid from the pump 23 also passes through conduit 24, valve 4 and conduit 3 into the upper portion of the cylinder I, where it acts upon the ram 2 so as to move the same downwardly. The fluid expelled by the ram 2 from the lower portion of the cylinder passes through the conduits 29 and 23 into the conduit 23 and from there to the suction side of the pump 25.

It may be assumed that the press ram 2 should come to a stop when a predetermined pressure is again passes through conduits 32 and 2| and 23 into the cylinders 33 and 33, respectively holding the plungers 3| and 34 in the position shown in the drawing. Furthermore, fluid delivered by the pump 25 passes through the conduits 24 and 23 into the lower portion, of the cylinder where it moves the ram 2 upwardly. The fluid' expelled from the upper portion of the cylinder passes in part through the conduits 3 and 23 into the suction line 23, and in part to the tank 21.

When the ram 2 has reached its fully retracted position, the cam 33 engages and closes the nor-' mally open limit switch 31, thereby establishing an energizing circuit for the solenoid l4, which circuit comprises the main supply line I2, switch 8T, which latter immediately closed as soon as it was released by the operator, line i3, solenoidi4, lines 3 and 33, switch 31, line 33, switch 4|, line 42 and the main supply line H. Energization of the solenoid I4 causes the valve member II to move toward the right, thereby again interrupting fluid connection between the conduits 2| and 23, while connecting the conduit 23 with the exhaust line 22. In the manner previously described, the pressure prevailing in the conduit 4 2, it is merely necessary to reverse the valve 4 exerted on the ram 2. In other words. the tonnage control valve 3 and switch 1 should be effective while the limit switch 41 should be inso as to establish fluid connection between the conduits 24 and 3, while connecting the conduits 23 and 23 with each other and, thereupon, to

open the starter switch ST for b reaking the energizing circuit for the solenoid M. The spring I! will then again move the valve member l5 into the position shown in Figure 1, and another working cycle will be performed, as previously described.

If it is desired to bring about energization of the solenoid 14 at the end of the downward stroke of the ram 2 in response to a predetermined position of the ram, rather than in response to a predetermined pressure exerted upon the said ram, it is merely necessary to open the switch 43, while closing the switch 45. It will then be clear that closure of the switch I cannot make the energizing circuit for the solenoid l4, whereas closure of the switch 41 by the cam 36 will close the energizing circuit for the solenoid l4.

Referring now to Figure 2, illustrating a modification of the servomotor means 30, 3!, 34, 33 of Figure 1, these servomotor means have, according to Figure 2, been replaced by a single cylinder 46 in which is reciprocably mounted a differential piston 49 connected through the piston rod 56 with the flow control member of the pump 25a, corresponding to the pump 25. The larger piston area of the piston 49 is located on the left side thereof, whereas the smaller area is located on the right side of the piston 49. A spring 5| continuously urges the piston 49 into its left hand end position.

The ends of the cylinder 48 are connected with conduits 32a and 23a, corresponding to the con-. duits 32 and 23 of Figure 1. The conduits 32a and 23a may be hooked up in the same manner as the conduits 32 and 23 are hooked up in Figure 1. will be substantially the same as the operation of the system shown in Figure 1. However, inasmuch as the left hand area of the piston 49 is larger than the right hand area thereof, the spring 5| has to be stronger than the spring 35, in order to maintain the piston 49 in its left hand end position during the operation as long as the pressure, acting on the left hand area of piston 49, remains below a predetermined value. However, when the pressure on the left hand area of the piston 49 reaches the said predetermined pressure, it will cause the piston 49 to move toward the right, thereby reducing the delivery of the pump and eventually shifting the pump into neutral or no delivery position. In other words, the device of Figure 2, in addition to performing the functions of the system shown in Figure 1, is also adapted to bring about movement of the pump into substantially neutral or no delivery position in response to a predetermined pressure at the pressure side of the pump.

Referring now to Figure 3, the system shown therein differs from that of Figure 1 primarily in that the variable delivery pump 25 has been replaced by a constant delivery pump 52. The suction side of the pump 52 is connected through conduit 53 with the fluid reservoir or tank 54, whereas the pressure side ,of the pump 52 is I connected through the conduit 55 with a cylinder 56 of a control valve, generally designated 51. Connected to the cylinder 56 is a cylinder 59, which is connected with the conduit 55 through a conduit 59. Branching off from the conduit 59 is a conduit 60 leading to a three-way valve 6|, corresponding to the three-way valve 16 of Figure 1.

The valve member 62 of the valve 6! is controlled by a solenoid 63 in the same manner as the valve member ii of Figure 1 is controlled by The operation of the device of Figure '2 the solenoid 14. A spring 64 continuously urges the valve member 62 toward the right for establishing fluid connection between the conduit 66 and the conduit 65, while preventing fluid connection between the conduit 66 and the conduit 65. When the solenoid 63 is energized, it shifts the valve member 62 toward the left so as to interrupt the fluid connection between the conduits 66 and 65, while connecting the conduit 66 with the conduit 65.

The conduit 65 leads to a cylinder 61 which is connected to the cylinder 56. Reciprocably mounted in the cylinder 56 is a valve member 68 with two pistonportions 69 and 70. The valve member 68 is continuously urged into its uppermost position by a spring H through the inter vention of a piston 12. A piston 13, reciprocably mounted in the cylinder 58 and of the same area as the piston 12, is adapted to be acted upon by fluid pressure in the line 53 for actuating the valve member 68 so as to move the same downwardly with regard to Figure 3.

The piston portions 69 and control the fluid -connection between the conduits 14, I5 and 16.

The conduit i4 leads into the conduit 53 and is connected through a conduit 11 with a four-way I valve 18, corresponding in its structure and function to the valve 4 of Figure 1. Also connected with the valve 18 are the conduit and the service conduits iia and 29a, corresponding to the conduits 3 and 29 of Figure 1. A choke I9 is provided in the conduit 16, which conduit is connected to the conduit 14.

Operation of second embodiment It may be assumed that the valve member 68 is in its neutral position, in which the piston portion I0 shuts off the conduit 15, while the conduits and 16 communicate with each other. It may furthermore be assumed that the solenoid 63 is energized so that the conduits 65 and 66 communicate with each other, while the conduit 66 is closed.

In order to start a cycle, the operator shifts the valve I8 into a position corresponding to the forward position of the. valve 4,- and dee'nergizes the solenoid 63 so that the spring 64 shifts the valve member 62 toward the right and establishes fluid connection between the conduits and 65. Pressure fluid delivered by the pump 52 will then pass' will pass through the conduits I1 and 14 into the conduit 59, this pressure acts upon the piston I3 and causes the same to move the valve member 68 into its lowermost position, in which the piston portion 10 closes the conduit '15, while the conduit 55 is connected with the conduit V5. The pump 52, therefore, now by-passes its delivery through the conduit 16 into the conduit 53 and no pressure fluid is delivered to the service lines 3a or 29a. In other words, the pump 52 now idles under minimum load, namely the load caused by the restriction of the choke 19, which restriction maintains only sufilcient pressure in the conduits 55 and 59 to hold the valve member 88 in its downward position against the thrust of the spring I1.

If it is now desired to supply pressure fluid into the service line 29a, the operator reverses the valve 18 so as to establish fluid connection between the conduits and 29a, while connecting the conduits 3a and H with each other. Furthermore, the solenoid 63 is deenergized so that the spring 64 returns the valve member 62 to its right hand position in the manner previously described. The valve member 88 will then be returned to its uppermost position and pressure fluid from the pump 52 will pass through conduit 15 into the service line 29a. The operation of the system will then be efiected in the manner described above.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a hydraulic system, a source oi fluid un der pressure, control means movable to vary the delivery of said source from zero to maximum, first means connected to respond topressure from said source to urge said control means toward zero delivery position, second means adapted to be connected to respond to pressure from said source to urge said control means to maximum delivery position against the action of said first means, said first and second means normally exerting equal opposed forces, continuously acting resilient means assisting the action of said second means, a valve movable into a first position to connect said second means to said source and into a second position to exhaust, a recipro- M cable ram connected to be actuated by fluid from said source, ram actuated means operable at the ends of the stroke thereof to move said valve into its second position, and manual means selectively operable to counteract said ram actuated means to return said valve to its first position.

2. In a hydraulic system, a variable delivery pump, a, fluid motor supplied thereby, control means for said pump movable between iull delivery and neutral positions, yielding means continuously urging said control means toward lull delivery position, opposed and equal fluid operable areas arranged in association with said control means one to assist said yielding means and the other to oppose, a continuous fluid connection between the discharge side of said pump and said other area, a valve movable into a first position to connect said one area with the discharge side oi said pump and into a second position to connect said one area with exhaust. yielding means continuously urging said valve toward its first position, means operable by said motor in a predetermined position thereoi for substantially instantaneously moving said valve into its second position, and manual means operable to counteract said last mentioned means.

GEORGE A WALDIE.

. REFERENCES CITED The following references are of record in the file of this patent:

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